The present invention relates to corrosion protection for gas turbine components, and in particular, to a process for providing corrosion protection for the internal components of a gas turbine in the complete flow path of gas or steam.
Gas turbines typically include components with parts that are made from iron. These parts typically include the internal bores of the casings, the rotor blades and spacers, combustion hardware and rotor bolting. These parts are critical components on gas turbines from a functional and performance standpoint. Typically, after a turbine has been assembled and tested, it is shipped to a location where it is either installed or stored for later installation. Often, during the time between a turbine leaving a manufacturing facility and its subsequent installation and startup at a power plant, the components of the turbine that include iron parts will rust. The development of rust on such component parts can significantly compromise the performance of the turbine. The rust can change the turbine's airfoil profile and thereby affect performance. Rust can also block up cooling holes and orifices. The presence of rust on a new turbine can also affect a customer's perception of the quality of the turbine being delivered and the ability of the turbine's manufacturer to deliver a satisfactory product.
There have been prior efforts to solve the problem of rust forming on iron turbine component parts. One method currently used to protect turbine components from the formation of rust involves stuffing paper impregnated with volatile corrosion inhibitors (“VCI”) into the inlet and exhaust cavities of the turbine to seal the cavities. VCI paper can help mitigate the beginning of corrosion, but must be kept dry. The problem with this method is that it provides corrosion protection only in the areas where the VCI paper is used.
Another method currently used involves installing a closed loop dehumidification system in the turbine to direct warm, dry air over the turbine's iron component parts. However, the effectiveness of this method is limited since it provides protection only to those turbine components directly in the flow path of the warm, dry air directed through the turbine by the dehumidification system. It does not protect any components that are not directly in the flow path of the warm, dry air. Thus, it would be desirable to provide a method of providing corrosion protection to all exposed surfaces of components inside the flow path of a turbine, such as casing walls and cavities, buckets, blades, nozzles, vanes, shafts, seals, combustors and cooling passages.